This invention relates to DC power supplies and in particular to a protective arrangement for a three-terminal IC power regulator used in such a DC power supply.
Three terminal adjustable voltage regulators in the form of integrated circuits (IC's) are known, for example the LM117, LM217 and LM317 of National Semiconductor, to name a few. These devices have an input terminal, an output terminal and an adjustment terminal and include built-in protective measures such as current limit, thermal overload protection and safe area protection. External diodes can be used to protect against damage caused by accidental capacitive discharges due to shorting the adjustment pin or output pin. However, they can be damaged or destroyed if the input-output differential exceeds their design limit, e.g. 40 volts.